Brillouin spectroscopy measurements on hybrid inorganic–organic materials obtained from aluminum and zirconium alkoxides

Brillouin spectroscopy was used for measuring the sound velocity through hybrid inorganic–organic polymeric materials obtained from the polymerization of 2-hydroxyethylmethacrylate (HEMA) modified by zirconium and aluminum alkoxides. Young’s modulus E, shear modulus G, bulk modulus B and Poisson’s ratio ν were calculated for the pure poly-HEMA, in a good agreement with the elastic constants measured by four point flexural experiments. The sound velocity measurements on the hybrid materials indicate that the elastic modulus of pure poly-HEMA is higher than those of the hybrids, almost irrespective of the concentration of inorganic compounds. This trend is confirmed by the results of the four points flexural tests performed on the same samples. The findings have been tentatively explained on the basis of the structural change in the polymeric network, due to the presence of the inorganic domains.